Seeping flow anti-clotting blood catheter

ABSTRACT

A catheter includes an elongated tube having a distal end and a proximal end. The elongated tube includes porous material having an interior and an exterior face. The interior face defines a lumen along a central axis of the elongated tube. The porous material is configured to flow a fluid between the interior face and the exterior face and to seep the fluid out of the porous material through the exterior face and interior face. A lining covers at least a portion of the exterior face and substantially limits perfusion through the exterior face at the portion of the exterior face covered by the lining. The catheter is impregnated with a material that prevents buildup of material on one of an inner face or an outer face of the catheter or the lining is coated with one or more of an anticoagulant, antibiotic, or antithrombotic.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 120 as a continuationof U.S. patent application Ser. No. 14/595,938 filed on Jan. 13, 2015and titled “SEEPING FLOW ANTI-CLOTTING BLOOD CATHETER” which claimspriority under 35 U.S.C. § 119(e) to U.S. Provisional Patent ApplicationNo. 61/927,325 filed on Jan. 14, 2014 and titled “SEEPING FLOWANTI-CLOTTING BLOOD CATHETER,” each of which is herein incorporated byreference in its entirety.

BACKGROUND OF THE DISCLOSURE

Catheters are tube-like medical devices that provide access to apatient. Catheters may be used to inject or remove agents, medications,or body fluids from a patient. Catheters can fail from extended periodsof use. The decreased performance of a catheter can be the result ofmaterial clogging the catheter. The clogs may be the result of debris orfrom the formation of clots or biofilms within the lumen of thecatheter.

SUMMARY OF THE DISCLOSURE

According to one aspect of the disclosure, a catheter includes anelongated tube having a distal end and a proximal end. The elongatedtube includes a porous material with an interior face and an exteriorface. The interior face defines a lumen along a central axis of theelongated tube. The porous material is configured such that a fluid canflow between the interior face and the exterior face of the porousmaterial and seep out of the porous material through the exterior faceand/or the interior face. The catheter also includes a first lining thatcovers at least a portion of the exterior face. The lining substantiallylimits perfusion through the exterior face at the portion covered by thefirst linings.

In some implementations, the catheter also includes a fitting coupled tothe proximal end of the elongated tube. The fitting is configured toflow a first fluid into the porous material and a second fluid into thelumen of the catheter. In some implementations, the first fluid isdifferent than the second fluid.

In certain implementations, the resistance to flow through the innerface or exterior face of the porous material is between about 10 andabout 100 times higher than the resistance to flow through the porousmaterial along an axis parallel to the central axis of the elongatedtube. In some implementations, the catheter includes a second liningthat covers at least a portion of the interior face. In someimplementations, the second lining covers substantially all of theinterior face except a portion toward the distal end of the elongatedtube. The first lining may cover substantially all of the exterior faceexcept a portion toward the distal end of the elongated tube.

In some implementations, the thickness of the porous material is betweenabout 20 μm and about 1 mm and the porous material includes phaseinversion polyethersulfone.

In some implementations, the interior face has a first porosity at afirst distance from the proximal end of the elongated tube and a secondporosity at a second distance from the proximal end of the elongatedtube.

According to another aspect of the disclosure, a method includesproviding a catheter for flowing a fluid. The catheter includes a porousmaterial having an interior face and an exterior face. The interior faceof the catheter defines a central lumen of the catheter. The method alsoincludes flowing a first fluid through the porous material of thecatheter and flowing a second fluid through the central lumen of thecatheter. In the method, the first fluid seeps into the central lumen ofthe catheter through the interior face of the porous material.

In some implementations, the method also includes flowing ananti-coagulant through the porous material of the catheter. The firstfluid can be flowed through the porous material at a pressure configuredto force the first fluid to seep through the interior face of thecatheter and into the central lumen of the catheter. In someimplementations, the method includes flowing the fluids through thecatheter at a pulsatile flow rate.

In some implementations, the method includes flowing a first agentthrough the central lumen of the catheter. In certain implementations, asecond agent, which counteracts the first agent, is flowed through theporous material of the catheter.

In some implementations, the porous interior face has a first porosityat a first distance from an inlet of the catheter and a second porosityat a second distance from the inlet of the catheter. In someimplementations, the method includes seeping the first fluid out of thecatheter through the external face of the porous material.

BRIEF DESCRIPTION OF THE DRAWINGS

The skilled artisan will understand that the figures, described herein,are for illustration purposes only. It is to be understood that in someinstances various aspects of the described implementations may be shownexaggerated or enlarged to facilitate an understanding of the describedimplementations. In the drawings, like reference characters generallyrefer to like features, functionally similar and/or structurally similarelements throughout the various drawings. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the teachings. The drawings are not intended to limitthe scope of the present teachings in any way. The system and method maybe better understood from the following illustrative description withreference to the following drawings in which:

FIG. 1 illustrates a schematic of system using an example seeping flowcatheter.

FIGS. 2A-2E illustrate cross-sectional views of example seeping flowcatheters with different lining configurations.

FIGS. 3A and 3B illustrate example tip configurations for a seeping flowcatheter.

FIG. 4 illustrates a seeping flow catheter with a plurality of liningconfigurations.

FIG. 5 illustrates micrographs of an example seeping flow catheter atvarious magnifications.

FIGS. 6A-6D illustrate front and cross-sectional views of examplemulti-lumen flow catheters.

FIG. 7 is a flow chart of an example method for seeping fluid into alumen of a catheter.

DETAILED DESCRIPTION

The various concepts introduced above and discussed in greater detailbelow may be implemented in any of numerous ways, as the describedconcepts are not limited to any particular manner of implementation.Examples of specific implementations and applications are providedprimarily for illustrative purposes.

FIG. 1 is a schematic of a system 100 using a seeping flow catheter 101.FIG. 1 provides a cross-sectional view of the catheter 101 and nozzle107. The catheter 101 is inserted into an internal lumen 102 of apatient. The internal lumen 102 can be any vessel, duct, or body cavityof the patient's body. Box 115 provides an enlarged view of a portion ofthe catheter 101 inserted into the internal lumen 102 of the patient.The catheter 101 includes a porous material 105. The porous material 105has an inner face 104 and the exterior face 106. The catheter's lumen103 is defined by the inner face 104 of the catheter 101. A nozzle 107injects fluid into the porous material 105 via a secondary fitting 108and into the lumen 103 via a primary fitting 109. A pump 110 flows fluidfrom the fluid reservoir 111 to the primary fitting 109, and a secondpump 112 flows fluid from the fluid reservoir 113 to the secondaryfitting 108. The pumps 110 and 112 are controlled by the controller 114.

The catheter 101 is described in greater detail in relation to FIGS.2A-5. Example methods of manufacture and uses of a seeping catheter aredescribed in relation to FIG. 7.

As an overview, the catheter 101 is a “seeping” catheter. The termseeping relates to a fluid seeping through the inner face 104 of theporous material 105 into the catheter's lumen 103 and/or out of thecatheter 101 through the exterior face 106 of the porous material 105 asfluid flows through the porous material 105 of the catheter 101. Asdescribed below, fluid seeping into the catheter's lumen 103 creates abarrier that reduces the interaction that a primary fluid (e.g., blood)flowing through the catheter's lumen 103 has with the inner face 104. Insome implementations, the barrier reduces the resistance to flow of theprimary fluid through the lumen 103 by altering the boundary conditionsand effectively increasing the internal diameter of the lumen 103. Insome implementations, the fluid seeping out of the exterior face 106reduces catheter 101 encapsulation. Encapsulation may occur when acatheter is in-dwelling for long periods of time in the patient's bodyand the patient's body begins to bond to, encapsulate, adhere clots orclotting agents to, adhere cells to, or endothelialize the catheter.Reducing encapsulation of the catheter 101 makes the catheter 101 easierto remove from a patient and increases patency duration. In someimplementations, encapsulation or thrombosis is reduced by seeping anagent out of the catheter 101. The agent can inhibit endothelializationor the buildup of other material within or on the catheter 101. In otherimplementations, the seeping flow washes away cell buildup on theexterior of the catheter 101. The seeping flow can be a continuous flowor a pulsed flow that is periodically passed through the catheter 101.In some implementations, the catheter 101 is impregnated with an agentthat passively prevents buildup of material on the inner face 104 or theexterior face 106. In some implementations, the agent impregnated intothe catheter 101 can include an inhibitor of clotting such as heparin orcitrate; a hydrophobic or hydrophilic surface modifier, a substance tochange the charge of the inner face 104, exterior face 106, or catheter101; a thrombolytic agent configured to dissolve buildup; or a proteaseconfigured to dissolve proteins

In some implementations, the porous material 105 is between about 20 μmand about 2 mm, between about 20 μm and about 1 mm, or between about 20μm and about 50 μm thick. In some implementations, the catheter 101 isthe same length of a standard medical catheter. In otherimplementations, the catheter 101 is coupled to a standard medicalcatheter and the catheter 101 portion of the catheter is between about 5cm and about 30 cm, between about 10 cm and 20 cm, or between about 5 cmand 15 cm long. In some implementations, the catheter 101 ismanufactured in the French catheter scale of between 1 gauge and 34gauge.

The system 100 also includes a nozzle 107 that injects fluid into thecatheter's lumen 103 and the porous material 105. The nozzle 107includes a primary fitting 109 to flow fluid into the catheter's lumen103, and a secondary fitting 108 to flow fluid into the catheter'sporous material 105. In some implementations, the nozzle 107 is based onthe port or Luer fittings commonly found in medical catheters and othermedical fluid flow devices. In some implementations, the primary fitting109 and the secondary fitting 108 are located at separate lengths alongthe catheter 101. For example, the secondary fitting 108 can be a collarthat wraps around the circumference of the catheter 101 at a specificlocation along the length of the catheter 101. The collar can injectfluid into the porous material 105 through the exterior face 106. Insome implementations, the secondary fitting 108 and the primary fitting109 flow fluid into their respective parts of the catheter 101 from asingle fluid source. In other implementations, as illustrated in FIG. 1,the secondary fitting 108 and the primary fitting 109 flow fluid intothe respective parts of the catheter 101 from different fluid sources.

The system 100 includes the first pump 110 and the second pump 112,which are connected to the first fluid reservoir 111 and the secondfluid reservoir 113, respectively. As described above, in someimplementations, a single pump and fluid reservoir is used to deliverfluid to the catheter's lumen 103 and the porous material 105. The pump112 and the pump 110 are controlled by the controller 114. Thecontroller 114 controls the rate, duration, and waveform of the fluidflow generated by the pumps 110 and 112. For example, the controller 114can cause the pumps 112 and 110 to flow fluid through the catheter 101at a substantially constant flow rate or in a pulsatile manner. In someimplementations, the controller 114 is also configured to control thepressure of fluids flowing within the porous material 105 and the lumen103. For example, a first fluid flowing through the porous material 105can be pressurized to a level higher than a second fluid flowing throughthe lumen 103 such the first fluid seeps into the lumen 103 and thesecond fluid does not seep into the porous material 105. In someimplementations, the flow rate of the fluid through the porous material105 is titrated such that the seeping flow into the lumen 103 of thecatheter 101 is between about 0.1% and about 5%, between about 5% andabout 30%, between about 10% and about 30%, or between about 20% andabout 30% of the flow rate of the fluid into the lumen 103 through theprimary fitting 109. In some implementations, a bolus or series ofpulses of the fluid flow is flowed through the porous material 105 to“debulk” the pores of the exterior face 106 and inner face 104. Forexample, as blood flows through the lumen 103 of the catheter 101, thepores of the inner face 104 can become clogged. The pulsatile flow canclear the pores of material such that fluid can continue to seep intothe lumen 103 of the catheter 101. In some implementations, the fluidseeps out of the porous material 105 after the fluid pressure in theporous material 105 has reached a predetermined threshold. In someimplementations, the controller 114 is configured to cause the pump 112to maintain a fluidic pressure in the porous material 105 above thepredetermined threshold.

In some implementations, the pumps 110 and 112 are infusion pumps,perfusion pumps, peristaltic pumps, or similar pumps used in combinationwith medical grade catheters. In some implementations, the pump 110 isused to create a vacuum such that the catheter 101 is used for fluidextraction from the patient. For example, the catheter 101 may be usedfor post-operative drainage. In this example, the pump 112 can stillinject a fluid into the porous material 105 such that the fluid seepsout of the porous material 105 to assist in the flow of the evacuatedfluid through the catheter 101 or to reduce encapsulation of thecatheter 101.

FIGS. 2A-2E illustrate cross-sectional views of example seepingcatheters with different lining configurations. As described above, thebody of the catheter 101 is defined by a porous material 105. As a fluidflows through the porous material 105, the fluid can seep out of thecatheter 101 through the exterior face 106 and inner face 104. In someimplementations, a lining is applied to the exterior face 106 and/orinner face 104 to reduce the permeability of the fluid through the faceto which the lining is applied.

FIG. 2A illustrates a cross-sectional view of an example seepingcatheter 200. The catheter 200 includes a lining 201 on the outer faceof the catheter 200. As illustrated no lining is applied to the innerface 202 of the catheter 200. The lining 201 can include a coating, suchas but not limited to adhesives or chemical vapor deposition coatingsthat when dried substantially limits perfusion through the areas towhich it is applied. In some implementations, heat or chemical solventsmay be applied to the face to create the lining. Heat or solvents createthe lining by melting the surface of the porous material, which sealsthe pores. In some implementations, the lining substantially prohibitsperfusion through the face to which it is applied. In otherimplementations, the lining reduces the perfusion through the face towhich it is applied when compared to the face without the application ofthe lining and in other implementations, the lining is configured toallow a predetermined level of perfusion through the applied face. Forexample, the lining may be configured to allow the perfusion ofmolecules below a specific molecular weight. In other implementations,the lining is selectively applied to specific areas to limit perfusionto various levels in those areas. In some implementations, the effect ofthe catheter 200 is created by using the porous material 203 as a liningfor the lumen of a standard catheter or, as in the below describedcatheter 240, a lining for the external face of a standard catheter. Insome implementations, the lining is coated with one or more of ananticoagulant, antibiotic, or antithrombotic.

As fluid flows through the porous material 203 of the catheter 200, thelining 201 substantially prevents the fluid from exiting the catheter200 through the outer face. Rather, the fluid seeps into the internallumen of the catheter 200 through the inner face of the catheter 200. Insome implementations, the fluid seeping into the internal lumen of thecatheter limits the interaction a primary fluid injected into the lumenvia the primary fitting 204 has with the inner face 202. Limiting theinteraction of the primary fluid and the inner face 202 changes theeffective boundary conditions of the primary fluid's flow through theinner lumen of the catheter 200. The change in effective boundaryconditions reduces the resistance to flow and increases the effectivediameter of the inner lumen. In some implementations, reducing theresistance to flow reduces pump losses when flowing fluids through thecatheter. When blood is flowed through the catheter, the reducedresistance can also reduce the potential of clotting or thrombusformation in the catheter.

In some implementations, the example catheter 200 is used to deliveragents to the primary fluid flowing through the lumen of the catheter200. The agents can include blood thinners, anti-coagulants, coagulants,medications, thrombolytics, antibiotics, antivirals, a dyes, labels, ortracing substances to allow visualization of the catheter or fluidflowing through it, a biological agents such as a proteins, peptides,DNA, RNA, RNAi, siRNA, or other nucleotide sequence, solutions to alterpH, solutions to alter compound concentrations in the blood, bindingagents to chelate or bind entities in the blood, dissolved or otherformats of gases such as oxygen, a capture agent to specificallytether/bind/capture an entity in the blood, an agent to alter theviscosity of a fluid in the lumen, toxin or an agent to counter a toxin,simple saline buffers or fluids, sugars, amino acids fats or othernutritive agents, inert molecules, volume expanders for the fluid in thelumen, any combination thereof, or agents to reverse (or counteract) oneor more of the foregoing agents. For example, a first catheterconfigured similarly to catheter 200 (or other implementation describedherein) may connect a patient to the input of a bypass machine and asecond catheter configured similarly to catheter 200 (or otherimplementation described herein) may return the blood to the patientfrom the bypass machine. The first catheter can introduce heparin, ablood thinner, into the blood such that it does not clot in the bypassmachine. Seeping protamine sulfate, a heparin reversal agent, into theblood as it returns to the patient via the second catheter reverses theeffects of the heparin in the blood. The protamine sulfate can beintroduced into the blood through the second catheter, such that reducedlevels, and in some implementations substantially no active heparinremains in the blood when it re-enters the patient's body. In anotherexample, where the catheter 200 is used as part of a urinary catheter,antibiotics may be seeped into the lumen of the catheter to limit theformation of bacterial biofilms that can form in, and clog, urinarycatheters and infect the patient.

FIG. 2B illustrates a cross-sectional view of an example seepingcatheter 220. Neither the exterior face 221 or inner face 222 arecovered with a lining. Thus, the fluid flowing through the porousmaterial seeps through the exterior face 221 and the inner face 222. Asin the catheter 200, the fluid seeping into the lumen through the innerface 222 can deliver an agent flowing through the lumen or be used toreduce the resistance to flow through the lumen. FIG. 2C describes theseeping of fluid through the outer face of a catheter and into thetissue surrounding the catheter.

FIG. 2C illustrates a cross-sectional view of an example seepingcatheter 240. The inner face of the catheter 240 includes a lining 241that substantially prevents fluid from seeping through the inner face ofthe catheter 240. The exterior face 242 is not coated with a lining toand thus fluid seeps out of the catheter 240 through the exterior face242 when fluid is flowed through the porous material of the catheter240. The extended placement of catheters can cause encapsulation of thecatheter and/or the catheter can become a source of infection. In someimplementations, the fluid seeping out of the exterior face 242 reducesencapsulation of the catheter 240. Encapsulation occurs when thepatient's body begins to endothelialize or otherwise encapsulate acatheter. Encapsulation can make it difficult or painful to remove thecatheter. The seeping of fluid through the exterior face 242 can limitthe interaction of the tissue surrounding the catheter 240 and thecatheter 240, reducing the occurrence of encapsulation. In someimplementations, encapsulation is reduced by the flowing a fluid throughthe porous material of the catheter 240 that includes agents to preventencapsulation. For example, agents that reduce vasculogenesis andangiogenesis can prevent endothelialization in an area local to thecatheter 240. In some implementations, agents such asanti-inflammatories or antibiotics are seeped into the surroundingtissue through the catheter 240. For example, seeping an antibiotic intothe tissue surrounding the catheter 240 to reduce the likelihood of aninfection occurring due to long term placement of an indwellingcatheter.

FIG. 2D illustrates a cross-sectional view of an example seepingcatheter 250. The catheter 250 includes interior porous material 251that seeps a fluid into the central lumen of the catheter and anexterior porous material 252 that seeps a fluid out of the catheter. Theinterior porous material 251 and exterior porous material 252 areseparated by a lining 253. In some implementations, the fluid flowedthrough the interior porous material 251 and the exterior porousmaterial 252 are different fluids and in other implementations thefluids are the same.

FIG. 2E illustrates a cross-sectional view of an example seepingcatheter 260. The catheter 260 includes a plurality of porous materials.The first porous material 261 extends a first length along the catheter260 and the second porous material 262 extends a second length along thecatheter 260. In some implementations, the first porous material 261 isused to seep a first fluid into the catheter 260 along a first length ofthe catheter 260 and then a second fluid is seeped into the catheter 260along a second length of the catheter through the second porous material262. For example, a blood thinner may be seeped into the catheter 260along a first length of the catheter 260 through the first porousmaterial 261 and then an agent to counteract the blood-thinner may beseeped into the catheter 260 through the second porous material 262before the blood enters a patient. In another implementation, the firstporous material 261 is configured on the exterior of the second porousmaterial 262 such that a first and second fluid can be seeped out of thecatheter 260 at different lengths along the catheter 260.

FIGS. 3A and 3B illustrate example tip configurations for a seepingcatheter. FIG. 3A illustrates a seeping catheter with an open tip 301.The open tip 301 enables the fluid flowing through the porous material302 to exit through the end of the catheter 300. For example, a salinesolution may be flowed through the porous material 302 to debulk buildupthat can occur near the tip of a catheter. In some implementations, boththe interior and exterior face of the porous material 302 are coveredwith a lining such that a fluid exits the porous material 302 throughsubstantially only the open tip of the catheter 300.

FIG. 3B illustrates a seeping catheter 320 with a closed tip 321. Theclosed tip 321 is sealed such that fluid does not exit through the endof the porous material 322. In some implementations, the closed tip 321may be formed by applying a lining, such as the lining described above,to limit perfusion through the inner face and outer face of thecatheter. In some implementations, a closed tip 321 design is used tocreate a pressure buildup of fluid within the porous material 322 suchthat the fluid in the porous material 322 can seep through inner orouter face of the catheter 320 upstream from the closed tip 321.

FIG. 4 illustrates an example seeping catheter 400 with a plurality oflining configurations. The catheter 400 is implanted through tissue 401.For example, the seeping catheter 400 may be implanted into theabdominal cavity of a patient and the tissue 401 may be the abdominalwall of the patient. The seeping catheter 400 is configured to have aplurality of lining configurations on both the exterior face 402 and theinner face 403. In the section 404, both the exterior face 402 and theinner face 403 are lined to substantially prevent perfusion through therespective faces of the catheter 400. The section 404 represents theexterior portion of the seeping catheter 400. In some implementations,the lining configuration of the section 404 causes the seeping catheter400 to behave like a standard catheter. For example, as with a standardcatheter, substantially no fluid leaks into the lumen of the seepingcatheter 400 or out through the exterior face 402 in the section 404 ofthe catheter 400.

In the section 405 of the seeping catheter 400, neither the exteriorface 402 or the inner face 403 are lined, allowing fluid to perfusethrough both the exterior face 402 and the inner face 403. In someimplementations, as described above, fluid perfusing through theexterior face 402 may reduce the likelihood of the seeping catheter 400becoming encapsulated by the tissue 401.

In the section 406 of the seeping catheter 400, the exterior face 402 islined. As illustrated, fluid from the porous material of the seepingcatheter 400 seeps into the internal lumen of the seeping catheter 400but not through the exterior face 402 of the seeping catheter 400. Asdescribed above, the lining configuration of the section 406 can be usedto introduce agents into the lumen of the catheter 400 and/or reduce theresistance to flow through the catheter 400.

At the tip 407, the exterior face 402 and the inner face 403 of thecatheter 400 are not lined. In some implementations, a tip configurationwith no lining enables the tip 407 of the catheter 400 to be debulked(i.e., material buildup near the tip 407 can be dislodged from thecatheter 400). As illustrated in FIG. 4, the lining configurationschange abruptly at the transition between sections. In someimplementations, the lining configurations change gradually. Forexample, along a length of a catheter, a lining may gradually becomethinner until it is substantially nonexistent. As the lining thins itallows a greater amount of perfusion through the face of the porousmaterial.

FIG. 5 shows micrographs of an example seeping catheter at variousmagnifications. Panel A of FIG. 5 illustrates a zoomed out view of thecatheter. As described below in relation to FIG. 7, in someimplementations, the seeping catheter is manufactured by rolling a sheetof porous material around a mandrel and the sealing the seam. Panel A ofFIG. 5 illustrates the rolled porous material prior to the sealing ofthe seam to create the tube structure of the seeping catheter.

Panel B of FIG. 5 illustrates an end of the catheter illustrated inPanel A of FIG. 5. Panel B of FIG. 5 illustrates the inner face 501, theporous material 502, and the exterior face 503 of the catheter. Panel Cof FIG. 5 is a micrograph of the boxed section in Panel B of FIG. 5under higher magnification. Panel C of FIG. 5 illustrates the porousnature of the porous material 502. Panel C of FIG. 5 also illustratesthat the exterior face 503 has been coated to create a lining that sealsthe porous material 502. Panel D of FIG. 5 is a micrograph illustratinga cutaway of the porous material 502. Panel D of FIG. 5 illustrates thepores that are created through the porous material 502, which enablefluid to flow substantially parallel to the central axis of thecatheter.

FIGS. 6A-6D illustrate front and cross-sectional views of examplemulti-lumen flow catheters. In some implementations, the multi-lumenflow catheters do not include an inner porous material. As illustratedin FIGS. 6A-6D, and described in greater detail below, the multi-lumencatheter includes concentric walls defining a hollow space therebetweenor a plurality of lumens running parallel (but not concentric) with oneanother. In some implementations, a fluid can be seeped (or flowed)through the inner face, outer face, catheter tip, or a combinationthereof. In some implementations, the walls of the multiple lumens aresubstantially non-porous, and the fluid flows between the inner face,outer face, or a combination thereof through ports manufactured therein.

FIG. 6A illustrates example front and cross-sectional views of anexample multi-lumen flow catheter 600 with parallel lumens. Catheter 600includes a primary lumen 601 and a secondary lumen 602. The primarylumen 601 and the secondary lumen 602 run parallel to one another andare non-concentric. The primary lumen 601 and the secondary lumen 602are in fluidic communication with one another through a port 604. Asillustrated in FIG. 6A, the port 604 is disposed toward the distal (orexit) tip 604 of the catheter 600. In some implementations, the tip 604of the catheter 600 can be flushed by flowing a fluid through thesecondary lumen 602. The fluid can be used to dislodge, flush, or clearmaterial that can accumulate at or toward the tip 604 of the catheter600. Having one or more ports 603 disposed toward the tip 604 of thecatheter 600 enables the tip 604 to be flushed via the secondary lumen602 with an inexpensive flushing agent (e.g., saline) rather than usingthe fluid within the primary lumen 601, which may be a costlytherapeutic fluid.

FIG. 6B illustrates example front and cross-sectional views of anexample multi-lumen flow catheter 610 with parallel lumens. The catheter610 includes a primary lumen 601 and a secondary lumen 602. The primarylumen 601 and the secondary lumen 602 run parallel to one another andare non-concentric. The primary lumen 601 and the secondary lumen 602are in fluidic communication with one another through a plurality ofports 604 that run along the at least a portion of a length of thecatheter 610. For example, the plurality of ports 604 may be disposedalong only about the last 1% to about the last 20% of the catheter 610or along substantially all of the catheter 610.

FIG. 6C illustrates example front and cross-sectional views of anexample multi-lumen flow catheter 620 with multiple lumens defined byconcentric walls. The catheter 620 includes a primary lumen 621 and asecondary lumen 622. The secondary lumen 622 is defined as the hollowspace between an inner wall 623 and an outer wall 624. The hollow space(e.g., the secondary lumen 622) is maintained by one or more ribs 625(also referred to as struts 625) that maintain the separation betweenthe inner wall 623 and the outer wall 624. Each of the ribs 625 have aheight between about 20 μm and about 2 mm, between about 20 μm and about1 mm, or between about 20 μm and about 50 μm thick. The inner wall 623terminates slightly prior to the tip 604 of the catheter 620. When theinner wall 623 terminates, fluid within the secondary lumen 622 entersthe primary lumen 621. In some implementations, the inner wall 623terminates at the tip 604 of the catheter 620, which causes the fluidwithin the secondary lumen 622 to exit at the tip of the catheter 620.In some implementations, the configuration illustrated in FIG. 6C isused to flush the tip of the catheter 620. In other implementations, theconfiguration is used to enable mixing of the fluids within the primarylumen 621 and the secondary lumen 622 substantially only toward the tip604 of the catheter 620. As illustrated, catheter 620 includes four ribsdistributed evenly about the circumference of the catheter 620. In someimplementations, each of the ribs 625 run substantially the entirelength of the catheter 620. In other implementations, each of the ribs625 runs only a portion of the length of the catheter 620 and thecatheter 620 includes a plurality of ribs 625 distributed about thecircumference of the catheter 620 at a plurality of locations along thelength of the catheter 620.

FIG. 6D illustrates an example front and cross-sectional view of anexample multi-lumen flow catheter 630 with multiple lumens defined byconcentric walls. The catheter 630 includes a primary lumen 621 and asecondary lumen 622. The spacing between an inner wall 623 and an outerwall 624 defines the secondary lumen 622. The spacing between the innerwall 623 and the outer wall 624 is maintained by a plurality of ribs625. Fluidic communication is provided between the primary lumen 621 andthe secondary lumen 622 via a plurality of ports 603 that run along alength of the catheter 630. In some implementations, the catheter 630can include a plurality of ports 603 distributed across the outer face624. The ports 603 distributed across the outer face 624 of the catheter630 can be in addition to or in place of the ports 603 distributedacross the inner face 623. In some implementations, a fluid flowingthrough the secondary lumen 622 exits through each of the ports 603 andcreates a fluidic barrier that reduces the resistance to flow of aprimary fluid through the primary lumen 621 by altering the boundaryconditions, effectively increasing the internal diameter of the primarylumen 621. In some implementations, a fluid flowing through ports 603distributed across the outer wall 624 can reduce encapsulation of thecatheter 630. In some implementations, a fluid within the secondarylumen 622 exits substantially only through the plurality of ports 603and in other implementations the fluid can also exit through the tip 604of the catheter 630. In any of the above described multi-lumen flowcatheters, one or more of the inner wall or outer walls can be apermeable membrane through which a fluid flowing through the secondarylumen can seep into the primary lumen and/or out of the catheter. In anyof the multi-lumen flow catheters described herein, the walls of thecatheter can include a thermoplastic, such as polystyrene,polycarbonate, polymethylmethacrylate, polyethersulfone, polysulfone,cyclic olefin copolymer, polyethylene; a cross-linked polymer, such aspolydimethylsiloxane (PDMS), polyurethane, polyimide; a polymermaterial, such as polystyrene, cellulose acetate (CA), CN, polysulfone(PS), polyether sulfone (PES), polyacrilonitrile (PAN), polyamide,polyimide, polyetherimide (PEI), polyvinylidene fluoride (PVDF),polyvinylchloride (PVC), high-molecular-weight polyethylene, Teflon,poly(vinyl pyrrolidone) (PVP), polyethylenglycol (PEG), tetronic 1307; acombination thereof; or any of the materials typically used to producecatheters.

FIG. 7 illustrates a flow chart of an example method 700 for seepingfluid into a lumen of a catheter. The method 700 includes providing aseeping catheter (step 701). The method 700 also includes flowing fluidthrough the lumen of the catheter (step 702) and flowing fluid throughthe porous material of the catheter (703). As fluid flows through theporous material, the fluid seeps into the lumen of the porous material(step 704).

As set forth above and referring to FIG. 1, the method 700 begins withthe provision of a seeping catheter (step 701). As described above, thecatheter 101 includes a porous material 105. The inner face 104 of theporous material 105 defines the lumen 103 of the catheter 101. Theporous material 105 also includes an exterior face 106.

In some implementations, the catheter is manufactured by rolling a sheetof porous material around a mandrel and then sealing the seam. In someimplementations, the porous material includes a polymer material, suchas polystyrene, cellulose acetate (CA), CN, polysulfone (PS), polyethersulfone (PES), polyacrilonitrile (PAN), polyamide, polyimide,polyetherimide (PEI), polyvinylidene fluoride (PVDF), polyvinylchloride(PVC), high-molecular-weight polyethylene, Teflon, or similar materialsthat create membranes through the phase inversion process. In someimplementations, the porous material includes a blend of polymers. Forexample, PES can be blended with poly(vinyl pyrrolidone) (PVP) orpolyethylenglycol (PEG). The porous material can also include surfacetreatments on linings such as tetronic 1307 and high-molecular-weightPEI. In some implementations, the porous material is manufactured byphase inversion of the polymer material. For example, the porousmaterial sheet may be manufactured by mixing the polymer material with asolvent. The polymer solution is then cast into the desired shape. Thecasting is then submerged in a bath of nonsolvent, which displaces thesolvent within the polymer casting. The release of the solvent from thepolymer leaves a porous material. In some implementations, the solventincludes supercritical carbon dioxide, N-methyl-2-pyrrolidone (NMP),Dimethyl sulphoxide (DMSO) methylene chloride/1,1,2-trichloroethane,2-methyl-2-butanol, dimethyl formamide, N,N-dimethylacetamide (DMAc),N,N-dimethylformamide (DMF), and triethyl phosphate (TEP).

In some implementations, the temperature of the bath, composition of thebath, the length of time the polymer casting is left in the bath, theinitial thickness of the polymer casting, the initial surfacecharacteristics of the polymer casting, the speed at which the polymercasting is extruded into and/or removed from the bath, and the ratio ofthe polymer to the solvent effect the porosity of the porous material.In some implementations, the porosity of the porous material isconfigured to limit, by molecular weight, the chemicals that can perfusethrough the porous material or its faces. In some implementations, theporous material is a commercially available permeable membrane, orcreated using similar materials and processes as commercially availablepermeable membranes. Example commercially available permeable membranescan include those by TangenX (Novasep), Pall, Millipore, Fresenius,Gambro, Asahi Kasei-Kuraray, Kawasumi, Nikkiso, JMS Co., Nipro, Toray,Membrana. In other implementations, the porous material is createdthrough an extrusion process.

In some implementations, one or more portions of the inner face andouter face are lined to substantially reduce the permeability of thelined portions. In some implementations, a lined face of the porousmaterial is about 10, about 100, about 1000, or about 10000 times lesspermeable when compared to an unlined face or the permeability along anaxis parallel to the central axis of the catheter. In someimplementations, substantially no flow occurs through a lined face ofthe porous material when compared to the flow through an unlined face orthe flow along an axis parallel to the central axis of the catheter. Insome implementations, an unlined face is about 10, about 100, about1000, or about 10000 times less permeable when compared to thepermeability along an axis parallel to the central axis of the catheter.In some implementations, the unlined portions of the porous materialhave a flux between about 0.1 ml/(min*mmHg*m̂2) and about 100ml/(min*mmHg*m̂2), between about 0.1 ml/(min*mmHg*m̂2) and about 5ml/(min*mmHg*m̂2), between about 5 ml/(min*mmHg*m̂2) and about 75ml/(min*mmHg*m̂2), between about 10 ml/(min*mmHg*m̂2) and about 50ml/(min*mmHg*m̂2), or about 25 ml/(min*mmHg*m̂2) and about 50ml/(min*mmHg*m̂2). In some implementations, the lining is created bycoating the face with an adhesive, chemical vapor deposition, orexposing the face to a solvent or heat. The lining seals the pores andsubstantially prevents fluid from seeping through the treated surface.

As described above, the seeping catheter is manufactured by rolling asheet of porous material around a mandrel and then sealing the seam. Insome implementations, the lining is applied to the sheet of porousmaterial prior to the porous material being rolled around a mandrel. Insome implementations, a mask is applied to the sheet of porous materialsuch that the lining is only applied to desired regions of the poroussheet. For example, to create a seeping catheter that is not linedtoward its exiting tip, a mask may be applied toward one end of a sheetof porous material that will become the exiting tip. The sheet of porousmaterial is then coated with an adhesive to form the lining. Once theadhesive has dried, the mask is removed. The adhesive was not able toreach the section of the sheet of porous material below the mask andthus that section of the porous sheet remains unlined. The sheet ofporous material is then rolled to create a seeping catheter. In someimplementations, a plurality of masks are used to create a plurality oflinings along the inner and/or outer face of the porous material. Insome implementations, the seeping catheter is manufactured by directlyextruding the polymer casting in a hollow circle cross section shapedirectly into the phase inversion bath. In other implementations, thecatheter is manufactured using a dry-wet spinning technique based onliquid-liquid phase separation. The method of manufacturing the catheteris selected responsive to the composition of the materials used to formthe catheter in some implementations.

Referring again to FIG. 7, the method 700 includes flowing fluid throughthe lumen of the catheter (step 702) and flowing fluid through theporous material of the catheter (step 703). The fluid is injected intothe porous material and the lumen of the catheter by a nozzle. Asdescribed in relation to FIG. 1, the nozzle 107 includes a secondaryfitting 108 that is configured to inject the fluid into the porousmaterial and a primary fitting 109 that is configured to inject thefluid into the lumen of the catheter. In some implementations, differentfluids are injected into the porous material and into the lumen of thecatheter. For example, blood may be flowed through the lumen of thecatheter and a saline solution containing a blood thinner are flowedthrough the porous material 105 of the catheter.

The method also include seeping fluid into the lumen (step 704). As thefluid flows through the porous material of the catheter, the fluid seepsinto the lumen of the catheter through the inner face of the catheter.In some implementations, the fluid also, or alternatively, seeps out ofthe catheter through the outer face of the catheter. As described inrelation to FIG. 4, in some implementations, the inner face and outerface can be configured differently along the length of the catheter. Forexample, at one point in the catheter the inner face and the outer faceof the catheter are lined such that fluid cannot seep out of the porousmaterial, but at a second location along the length of the catheter theinner face may not be lined such that fluid can seep into the lumen ofthe catheter.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The forgoingimplementations are therefore to be considered in all respectsillustrative, rather than limiting of the invention.

What is claimed is:
 1. A catheter comprising: an elongated tube having adistal end and a proximal end, the elongated tube comprising a porousmaterial having an interior face and an exterior face, the interior facedefining a lumen along a central axis of the elongated tube, the porousmaterial being configured to flow a fluid substantially parallel to thecentral axis between the interior face and the exterior face of theporous material and to seep the fluid out of the porous material throughthe exterior face and interior face; a lining covering at least aportion of the exterior face and substantially limiting a perfusionthrough the exterior face at the portion of the exterior face covered bythe lining; and one or more of: the catheter being impregnated with amaterial that prevents buildup of material on one of an inner face or anouter face of the catheter; and the lining being coated with one or moreof an anticoagulant, antibiotic, or antithrombotic.
 2. The catheter ofclaim 1, wherein the resistance to flow through the inner face orexterior face of the porous material is between about 10 and about10,000 times higher than the resistance to flow through the porousmaterial along an axis parallel to the central axis of the elongatedtube.
 3. The catheter of claim 2, wherein the interior face has a firstporosity at a first distance from the proximal end of the elongated tubeand a second porosity at a second distance from the proximal end of theelongated tube.
 4. The catheter of claim 2, wherein the thickness of theporous material is between about 20 μm and about 1 mm.
 5. The catheterof claim 4, further comprising an open tip.
 6. The catheter of claim 4,further comprising a closed tip.
 7. The catheter of claim 1, wherein thematerial includes one or more of an inhibitor of clotting, a hydrophobicsurface modifier, a hydrophilic surface modifier, a substance to changea charge of one of the inner face or outer face of the catheter, athrombolytic agent, or a protease.
 8. The catheter of claim 1, furthercomprising a fitting coupled to the proximal end of the elongated tube,the fitting configured to flow a first fluid into the porous materialand a second fluid into the lumen, the fitting including a collardisposed about a circumference of the catheter and configured to injectthe first fluid into the porous material through the exterior face ofthe porous material.
 9. The catheter of claim 1, wherein the elongatedtube includes an unlined section extending from a section of theelongated tube having the exterior face covered by the lining.
 10. Asystem comprising: the catheter of claim 1; a primary fitting configuredto inject a fluid into the lumen of the catheter; a fluid reservoirincluding the fluid; a pump configured to flow the fluid from the fluidreservoir through the primary fitting into the lumen of the catheter;and a controller configured to control the pump.
 11. The system of claim10, further comprising: a secondary fitting configured to inject asecond fluid into the porous material; a second fluid reservoirincluding the second fluid; and a second pump configured to flow thesecond fluid from the second fluid reservoir through the secondaryfitting into the porous material, the second pump being controlled bythe controller.
 12. The system of claim 11, wherein the controller isconfigured to cause one of the pump and the second pump to flow fluidthrough the catheter in a pulsatile manner.
 13. The system of claim 11,wherein the primary fitting and secondary fitting are located atseparate lengths along the catheter.
 14. The system of claim 13, whereinthe fluid reservoir and the second fluid reservoir are the samereservoir.
 15. The system of claim 14, wherein the fluid and the secondfluid are the same fluid.
 16. The system of claim 13, wherein thecontroller is configured to pressurize the fluid flowing through thelumen to a different pressure than the second fluid flowing through theporous material.
 17. The system of claim 11, wherein the pump isconfigured to create a vacuum to draw fluid from a patient through thecatheter.
 18. The system of claim 17, wherein the second pump isconfigured to inject the second fluid in to the porous material and seepthe second fluid out of the porous material while the pump creates thevacuum to draw the fluid from the patient.
 19. The system of claim 11,wherein the second fluid includes one or more of a blood thinner, ananti-coagulant, a thrombolytic agent, a medication, an antibiotic, anantiviral, a dye, a label, a tracing substance, a protein, a peptide,DNA, RNA, RNAi, or siRNA, a coagulant, or an agent to reverse (orcounteract) one or more of the foregoing agents.
 20. The system of claim11, wherein the second fluid includes one or more of solutions to alterpH, solutions to alter compound concentrations in blood, binding agentsto chelate or bind entities in blood, dissolved or other formats ofgases, a capture agent to specifically tether/bind/capture an entity inblood, an agent to alter viscosity of a fluid in the lumen, toxin, anagent to counter a toxin, simple saline buffers or fluids, sugars, aminoacids fats or other nutritive agents, inert molecules, volume expandersfor the fluid in the lumen, or an agent to reverse (or counteract) oneor more of the foregoing agents.